1.Prepositional phraseBeing taken care of or being addressed.
"Don't worry; the police have been called and the situation is under control."
2.Prepositional phraseBeing actively controlled, or able to be actively controlled in its current state.
"Throughout the turbulence encounter, the pilots kept the aircraft under control.; The control rods absorb neutrons in the reactor core, keeping the fission reaction under control and preventing it from going prompt critical."